首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6107篇
  免费   609篇
  国内免费   400篇
耳鼻咽喉   11篇
儿科学   41篇
妇产科学   16篇
基础医学   271篇
口腔科学   51篇
临床医学   898篇
内科学   700篇
皮肤病学   21篇
神经病学   493篇
特种医学   70篇
外科学   177篇
综合类   749篇
现状与发展   3篇
一般理论   1篇
预防医学   637篇
眼科学   43篇
药学   1467篇
  8篇
中国医学   1370篇
肿瘤学   89篇
  2024年   36篇
  2023年   148篇
  2022年   206篇
  2021年   334篇
  2020年   303篇
  2019年   339篇
  2018年   274篇
  2017年   317篇
  2016年   293篇
  2015年   259篇
  2014年   432篇
  2013年   623篇
  2012年   386篇
  2011年   392篇
  2010年   257篇
  2009年   246篇
  2008年   265篇
  2007年   265篇
  2006年   237篇
  2005年   194篇
  2004年   159篇
  2003年   155篇
  2002年   137篇
  2001年   131篇
  2000年   79篇
  1999年   55篇
  1998年   74篇
  1997年   78篇
  1996年   48篇
  1995年   43篇
  1994年   44篇
  1993年   39篇
  1992年   37篇
  1991年   25篇
  1990年   20篇
  1989年   21篇
  1988年   19篇
  1987年   16篇
  1986年   11篇
  1985年   20篇
  1984年   18篇
  1983年   13篇
  1982年   13篇
  1981年   10篇
  1980年   11篇
  1979年   7篇
  1978年   5篇
  1977年   6篇
  1976年   10篇
  1975年   3篇
排序方式: 共有7116条查询结果,搜索用时 15 毫秒
151.
观察妥布霉素伤用凝胶的体外抗菌活性 ,为临床应用提供试验依据。采用平皿二倍稀释法测定了妥布霉素伤用凝胶对临床分离的 12 0株临床常见的革兰氏阳性及革兰氏阴性菌的体外抗菌作用。以对青霉素敏感的金葡菌、表葡菌、对庆大霉素敏感的大肠杆菌、敏感绿脓杆菌的作用为最强 ,MIC50 均为 0 2 5mg/L。妥布霉素伤用凝胶抗菌谱较广 ,对试验中的革兰氏阳性及革兰氏阴性菌均具有较强的杀灭或抑制作用 ,显示出较好的抗菌活性。  相似文献   
152.
目的:分析在校大学生预防自杀意念的外在保护因素。方法:采用分层抽样、三阶段抽样等方法,应用NCS-R自杀意念量表,对某北京高校两个学年的大学生(n=1256)的学习与生活状况进行调查,并进行logistic回归分析。结果:在校大学生有自杀意念的有173人(占13.77%);积极参加班级活动、经常参加体育锻炼等则是大学生群体减少自杀意念的保护因素,差异有统计学意义(均P<0.05)。结论:积极参加班级课外活动及体育锻炼对预防自杀意念有正向影响,建议作为大学生自杀预防的外在保护因素而加以重视。  相似文献   
153.
There is a significant need for high-quality medical physics education and training in all countries to support effective and safe use of modern medical technology for both diagnostic and treatment purposes. This is, and will continue to be, achieved using appropriate technology to increase both the effectiveness and efficiency of educational activities everywhere in the world. While the applications of technology to education and training are relatively new, the successful applications are based on theories and principles of the learning process developed by two pioneers in the field, Robert Gagne and Edgar Dale.The work of Gagne defines the different levels of learning that can occur and is used to show the types and levels of learning that are required for the application of physics and engineering principles to achieve appropriate diagnostic and therapeutic results from modern technology. The learning outcomes are determined by the effectiveness of the learning activity or experience. The extensive work of Dale as formulated in his Cone of Experience relates the effectiveness to the efficiency of educational activities. A major challenge in education is the development and conduction of learning activities (classroom discussions, laboratory and applied experiences, individual study, etc) that provide an optimum balance between effectiveness and efficiency. New and evolving models of the educational process use technology as the infrastructure to support education that is both more effective and efficient.The goal is to use technology to enhance human performance for both learners (students) and learning facilitators (teachers). A major contribution to global education is the trend in the development of shared educational resources. Two models of programs to support this effort with open and free shared resources are Physical Principles of Medical Imaging Online (http://www.sprawls.org/resources) and AAPM Continuing Education Courses (http://www.aapm.org/international).  相似文献   
154.

Introduction

Mobile phone conversation decreases the ability to concentrate and impairs the attention necessary to perform complex activities, such as driving a car. Does the ringing sound of a mobile phone affect the driver''s ability to perform complex sensory-motor activities? We compared a subject''s reaction time while performing a test either with a mobile phone ringing or without.

Material and methods

The examination was performed on a PC-based reaction time self-constructed system Reactor. The study group consisted of 42 healthy students. The protocol included instruction, control without phone and a proper session with subject''s mobile phone ringing. The terms of the study were standardised.

Results

There were significant differences (p < 0.001) in reaction time in control (597 ms), mobile (633 ms) and instruction session (673 ms). The differences in female subpopulation were also significant (p < 0.01). Women revealed the longest reaction time in instruction session (707 ms), were significantly quicker in mobile (657 ms, p < 0.01) and in control session (612 ms, p < 0.001). In men, the significant difference was recorded only between instruction (622 ms) and control session (573 ms, p < 0.01). The other differences were not significant (p > 0.08). Men proofed to complete significantly quicker than women in instruction (p < 0.01) and in mobile session (p < 0.05). Differences amongst the genders in control session was not significant (p > 0.05).

Conclusions

The results obtained proofed the ringing of a phone exerts a significant influence on complex reaction time and quality of performed task.  相似文献   
155.
The fragile X syndrome, fragile X tremor ataxia syndrome, and premature ovarian insufficiency are conditions related to the X chromosome folate-sensitive fragile site FRAXA. Therefore, we propose that they are considered as a family of disorders under the general designation of FRAXopathies. The present review will outline the main clinical and molecular features of these disorders, with special emphasis on the pathogenic mechanisms that lead to distinct phenotypes, starting from related mutations. The understanding of these mechanisms is already generating promising therapeutic approaches.  相似文献   
156.

Objectives

International literature suggests that arts and culture activities may benefit mental health, however, such survey studies conducted in the Danish population are scarce. Further, studies have investigated the associated risk for incident depression, but not for persistent depression. The objective of the current prospective study was to assess associations of engagement in arts and culture activities with incident/persistent depression and also mental wellbeing among Danish adults in the general population.

Design

Observational prospective study.

Methods

Data stem from a Danish nationally representative panel study of 5000 adults (aged 15+ years) conducted in 2019 and 2020, which was linked to Danish register data. An exposure variable was constructed for frequency of attending concerts, theatres, museums, and cinemas. Validated scales were used to assess the presence of depression (PHQ-8) and levels of mental wellbeing (SWEMWBS). Binary logistic regression analyses were conducted to assess the risk of incident depression (among participants free of depression at baseline), as well as the risk of persistent depression (among participants with depression at baseline), while multinomial logistic regression was used to assess odds for moderate and high mental wellbeing (low as base outcome) while adjusting for baseline values.

Result

In terms of incident depression, quarterly engagement in arts and culture activities (compared to never) was associated with an OR of .43 (95%CI .23–.80), while 8 times or more was associated with an OR of .53 (.29–.97). In terms of persistent depression, quarterly engagement was associated with an OR of .30 (.10–.90), while 8 times per year or more was associated with an OR of .26 (.07–.92). Similar to the patterns for incident/persistent depression, associations with moderate mental wellbeing showed higher odds for quarterly engagement and 8 times per year or more. Quarterly engagement was also associated with higher odds for high mental wellbeing but did not reach statistical significance.

Conclusions

The results support the involvement of the cultural and creative sectors in health strategies. Mental health promotion initiatives as well as arts and culture sectors may encourage the general public to engage in arts and culture activities with frequencies of at least once per quarter.  相似文献   
157.
In crustaceans, anti-lipopolysaccharide factors (ALFs) are important immune effectors that have sequence diversity and exhibit broad antimicrobial activities. In this study, we characterized a novel ALF homolog SpALF6 from mud crab Scylla paramamosain and its variant SpALF6-V, which was generated by mutations of two amino acids (H46 to R and A110 to P) due to the presence of two single nucleotide polymorphisms (SNPs). SpALF6 was an anionic peptide with isoelectric point (pI) 6.79, whereas SpALF6-V was a cationic protein with pI 7.98. These two proteins shared a common lipopolysaccharide (LPS)-binding domain (LBD) with pI 6.05. SpALF6 was expressed mainly in hemocytes and up-regulated by Vibrio parahaemolyticus or Staphylococcus aureus challenge, indicating that SpALF6 may participate in the antibacterial immune responses. To investigate the likely functional differences between SpALF6 and SpALF6-V and elucidate the underlying mechanisms, a single amino acid mutant SpALF6-M (from H46 to R, outside but very close to LBD), which had the same pI as SpALF6-V, was harvested by a fusion PCR. Then, both SpALF6 and SpALF6-M were overexpressed and purified to test antimicrobial activity and binding activity to microbial cells or polysaccharides. SpALF6-M exhibited more potent antimicrobial and cell-binding activity on Gram-positive bacteria and fungi than SpALF6. Furthermore, SpALF6-M possessed stronger lipoteichoic acid (LTA)-binding activity than SpALF6, demonstrating that this particular positively charged amino acid outside but close to LBD contributed to the increase in SpALF6-M antibacterial activity. In addition, SpALF6 LBD peptide and its biotin-labeled form were synthesized in this study. Results showed that this anionic LBD peptide itself did not exhibit any significant antimicrobial activity against 10 kinds of microorganisms but it possessed strong binding activity to LPS, LTA, and peptidoglycan. These findings suggested that this anionic LBD was still an important active center and required collaboration with some particular positively charged amino acids outside LBD to exhibit antibacterial activity. Thus, SpALF6-M antimicrobial activity was increased by the mutation of H46 to R instead of A110 to P, which did not change the protein charge, suggesting that SpALF6-V may have more potent antimicrobial activity than SpALF6 and play more important roles in antibacterial immunity. This study provided a new insight into the mechanisms of how ALF amino acid sequence diversity resulted in their functional divergence.  相似文献   
158.

Background

The purpose of the study was to determine whether prefabricated foot orthoses immediately reduce pain during functional tasks in people with patellofemoral osteoarthritis, compared to flat insoles and shoes alone.

Methods

Eighteen people with predominant lateral patellofemoral osteoarthritis (nine women; mean [SD] age 59 [10] years; body mass index 27.9 [3.2] kg/m2) performed functional tasks wearing running sandals, and then wearing foot orthoses and flat insoles (random order). Participants rated knee pain during each task (11-point numerical rating scales), ease of performance and knee stability (five-point Likert scales), and comfort (100 mm visual analogue scales).

Results

Compared to shoes alone, foot orthoses (p = 0.002; median difference 1.5 [IQR 3]) and flat insoles (p < 0.001; 2 [3]) significantly reduced pain during step-downs; foot orthoses reduced pain during walking (p = 0.008; 1 [1.25]); and flat insoles reduced pain during stair ambulation (p = 0.001; 1 [1.75]). No significant differences between foot orthoses and flat insoles were observed for pain severity, ease of performance or knee stability. Foot orthoses were less comfortable than flat insoles and shoes alone (p < 0.05).

Conclusions

In people with patellofemoral osteoarthritis, immediate pain-relieving effects of prefabricated, contoured foot orthoses are equivalent to flat insoles. Further studies should investigate whether similar outcomes occur with longer-term wear or different orthosis designs.  相似文献   
159.
The methanolic extract and conessine isolated from the stem bark of Holarrhena floribunda (Hf) were tested for their antibacterial activities on Bacillus: Bacillus cereus, Bacillus subtilis, Bacillus megaterium and Bacillus stearothermophilus using the disc diffusion method. Phytochemical analysis of the crude extract and fractions was also conducted. The inhibition parameters of the crude methanol extract and the total alkaloid fraction were determined using the macrodilution method. The results showed that the crude extract, the total alkaloid fraction and conessine exhibited a significant antibacterial effect against all the strains studied. The antibacterial effect of conessine is almost similar to that of chloramphenicol used as reference. The ratio of the minimal bactericidal concentration (MBC) over the minimal inhibitive concentration (MIC) indicates the bactericidal effect of the plant. These results support common use of stem bark of Hf and conessine isolated from Hf in the treatment of some infectious diseases.  相似文献   
160.
Abstract

The use of wearable recorders for long-term monitoring of physiological parameters has increased in the last few years. The ambulatory electrocardiogram (A-ECG) signals of five healthy subjects with four body movements or physical activities (PA)—left arm up down, right arm up down, waist twisting and walking—have been recorded using a wearable ECG recorder. The classification of these four PAs has been performed using neuro-fuzzy classifier (NFC) and support vector machines (SVM). The PA classification is based on the distinct, time-frequency features of the extracted motion artifacts contained in recorded A-ECG signals. The motion artifacts in A-ECG signals have been separated first by the discrete wavelet transform (DWT) and the time–frequency features of these motion artifacts have then been extracted using the Gabor transform. The Gabor energy feature vectors have been fed to the NFC and SVM classifiers. Both the classifiers have achieved a PA classification accuracy of over 95% for all subjects.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号